Electrohydraulic brake systems are widespread in motor vehicles. Brake systems are known, for example, from DE 10 2010 062 387 A1, which is incorporated by reference, and comprise a main brake cylinder, a vacuum brake booster which is arranged upstream of the main brake cylinder and an electrohydraulic ABS/ESP brake control device, wherein the brake control device comprises pressure control valves and an electrically controllable pump for adjusting wheel-specific brake pressures. The four wheel brakes are connected to the wheel-specific output pressure connections of the brake control device. By means of the pump, an active, remote-controlled build-up of brake pressure is possible, whereby brake pressure control functions such as the traction control system (TCS) and electronic stability program (ESP) are enabled.
It is to be anticipated that there will also be used in future vehicle brake systems which are suitable for automatically driven vehicles. These brake systems must in principle be systems which can be controlled remotely. This means that a brake request is requested by means of electronic or electrical control signals and can be implemented by the system without any action from the driver. In this instance, a sufficiently high availability of the brake system or the brake function which can be remotely controlled must be ensured for safety reasons.
In the brake systems of DE 10 2010 062 387 A1, in the event of failure of the brake control device, a remotely controlled (driver-independent) build-up of brake pressure and a wheel-specific brake pressure control (for example, anti-lock braking system (ABS)) are no longer possible. Such a brake system is therefore less suitable for motor vehicles which are driven in a highly automated or independent manner.
For highly automatic or highly automated driving (HAD), it is not possible to switch off the brake system after any initial error. In the event of failure of an electronic control device which is associated with the independent driving, it is intended that, at least for a predetermined period of time (for example, a few seconds), a functional independent brake function and steering function can still be constituted since it must not be assumed that the driver can take over control of the vehicle immediately after a failure of the control device, but instead first has to be asked to resume driving operation and has to prepare for this.